• Preheat the oven to 350º F. Spray a 9 inch round cake pan or pie pan with nonstick cooking spray and line with a parchment paper circle. Set aside.
• In a mixing bowl combine the flour, cornstarch, baking soda, salt, and ¾ cup of chocolate chips. Save the remaining ¼ cup of chocolate chips for the top of the cake. Set aside.
  1 ½ cups (180g) all-purpose flour, 1 tsp cornstarch, ½ tsp baking soda, ¼ tsp salt, 1 cup (170g) semi-sweet chocolate chips
• In a larger mixing bowl combine the butter, brown sugar, and granulated sugar. Beat on medium speed for 1 minute. You want this mixture to be fluffy and pale in color.
  ½ cup (113g) unsalted butter, ⅔ cup (142g) brown sugar, 2 Tbsp granulated sugar
• Add in the egg and vanilla extract, beat for 30 seconds.
  1 large egg, 1 tsp vanilla extract
• Gradually mix in the dry ingredients, mixing on low speed. The dough will be very thick.
• Spray your hands with nonstick cooking spray and press the dough into an even layer in the pan. Press the remaining ¼ cup chocolate chips onto the top. Bake for 20-25 minutes or until the top of the cake turns golden in color and the edges are set. Remove from the oven and allow the cake to cool completely before removing from the pan.
• Use a thin spatula to loosen the sides of the cake, then turn it upside down and tap the bottom of the pan until the cake releases. Place the cookie cake on a serving plate.

Frosting

• Place the room temperature unsalted butter in a mixing bowl. Use an electric mixer on medium and beat the butter for 30-60 seconds, until whipped and fluffy.
  ½ cup (113g) unsalted butter
• Add in the cocoa powder, powdered sugar, vanilla extract and salt, beat again on low for 1-2 minutes, scraping down the sides of the bowl, until everything is incorporated.
  ⅓ cup (28g) unsweetened cocoa powder, 1 cup (113g) powdered sugar, 1 tsp vanilla extract, ⅛ tsp salt
• If the frosting is too thick, add a tablespoon of milk or heavy cream, and beat until creamy.
  dash milk or heavy cream if frosting becomes too thick
• Transfer the frosting to a piping bag fit with a piping tip and decorate the cookie cake as desired.